In 1834, he became pastor of Union Congregational Church in Boston, Massachusetts. He would remain in that position through 1878. In 1850, he married again, to Sarah Brackett.

In 1854, he took a trip to the American South, and wrote a book entitled A South-Side View of Slavery (Boston, 1854). This book was one of several polemic works he wrote. It caused a great sensation, and he received much hostile criticism. The book was attacked by abolitionists for its perceived moderation. In the book, he lauded slavery as beneficial to the Negroes' religious character.[1][2] In 1861, Adams wrote a successor volume, The Sable Cloud, a Southern tale with Northern Comments, to answer his attackers, and it was met with a similar response.

He also wrote The Cross in the Cell, Scriptural Argument for Endless Punishment, Broadcast, At Eventide, and a Life of John Eliot.[2] He was a member of the American Tract Society and the American Board for Foreign Missions.

In 1869, in consequence of his failing health, his people procured an associate pastor and gave Adams a long leave of absence. He made a voyage round the world and described it in Under the Mizzenmast (1871). He died in 1878, aged 72. He left nine children.